HAL Portal UBS (Université Bretagne Sud)
Not a member yet
14201 research outputs found
Sort by
On the crack propagation along brittle viscoelastic adhesive layer in DCB test
No full textInternational audienceThe mechanical behaviour of adhesives is known to be sensitiveto the deformation rate. The dependence of the critical StrainEnergy Release Rate (SERR) in bonded joints on the crack propagationrate has been widely reported in the literature.Typically, the evolution of the critical SERR with respect to thecrack propagation rate is often presented as a “master curve”,without specifying the necessary conditions that ensure thegeneralization and transferability of the findings. In this context,the present work provides a theoretical analysis of the DCB testin the presence of a brittle viscoelastic interface. A Euleriandescription is employed to describe the steady-state crack propagationregime. The results are then compared to thoseobtained from more comprehensive Lagrangian simulations ofthe DCB test. The analysis reveals that the evolution of thecritical SERR depends not only on the crack propagation ratebut also on the instantaneous boundary and loading conditions.This indicates that the critical SERR cannot be regarded as anintrinsic property of a viscoelastic interface. These results alsothe discussion on the specific treatment of the crack initiationand propagation regimes.<br /
Monuments ou champs de bataille ? Honorer les morts hors de Bretagne durant l’entre-deux-guerres
No full textInternational audienceFar from Brittany, numerous monuments honor the Bretons who fell in combat. This is true in places like Attichy and Moulin-sous-Touvent in France, as well as in Belgium at Arsimont, Boesinghe, Maissin, Auvelais, and Saint-Charles-de-Potyze. These monuments quickly became part of the landscape of memorial tourism, which developed shortly after the war ended. But how are these distant monuments perceived by the Bretons? This article, focusing on the interwar period, explores the role of these monuments and the perspectives of visitors from the Armorican peninsula, whether pilgrims or tourists. Do these visits serve as a personal tribute to a fallen loved one, or are they part of a broader collective memory of the conflict?Loin de la Bretagne, de nombreux monuments honorent les Bretons tombés au combat. C’est le cas à Attichy et à Moulin-sous-Touvent ; ou encore en Belgique, à Arsimont, à Boesinghe, à Maissin, à Auvelais et à Saint-Charles-de-Potyze. Ces derniers trouvent très rapidement leur place dans le cadre du tourisme mémoriel qui se développe dès la fin du conflit. Or, comment ces édifices lointains sont-ils perçus par les Bretons ? Cet article, centré sur l'Entre-deux-guerres, examine le rôle de ces monuments et leurs visiteurs venus de la péninsule armoricaine, qu'ils soient pèlerins ou touristes. Ces visites relèvent-elles d’un hommage à un proche disparu ou participent-elles d'une mémoire collective du conflit
Recommendation of TC RILEM TC 274-TCE: 3-point bending test procedure for earthen bricks—quality control of earth bricks for structural masonry by flexural strength
No full textInternational audienceBuilding with unstabilised earth bricks (EB) as units for structural masonry walls offers a sustainable alternative to mitigate resource depletion's negative impact and global warming. Using locally sourced earth for EB production is required to achieve these benefits. This leads to large variations in material composition. Consequently, quality control becomes critical to ensure adequate mechanical performance of the masonry units. In the framework of the RILEM TC 274-TCE, the characterisation of the flexural strength of bricks has been examined. A comprehensive inter-laboratory campaign involving seven laboratories across three countries was conducted, during which flexural tests were performed on 98 bricks. This article details the TC 274-TCE recommendations on the procedure to conduct a 3-point bending test on an EB. Key test parameters such as specimen pre-conditioning, setup boundary conditions, loading rate and determination of material flexural strength are discussed. The calculation of flexural strength was evaluated by comparing results obtained from the beam theory model and a solid mechanics approach, validated through finite element modelling. The findings confirm that the 3-point bending test is a reliable method to assess the mechanical performance of EB and to control their quality
Eco-friendly cellulose paper composites: A sustainable solution for EMI shielding and green engineering applications
No full textCellulose paper-based composites represent a promising and sustainable alternative for electromagnetic interference (EMI) shielding applications. Derived from renewable and biodegradable cellulose fibers, these composites are enhanced with conductive fillers namely carbon nanotubes, graphene, or metallic nanoparticles, achieving efficient EMI shielding while maintaining environmental friendliness. Their lightweight, flexible nature, and mechanical robustness make them ideal for diverse applications, including wearable electronics, flexible circuits, and green electronics. This paper explores the fabrication techniques, composite properties, with particular emphasis on ways to enhance the shielding properties, and performance metrics of cellulose-based composites, highlighting their potential to replace traditional metallic materials in various EMI shielding scenarios, thus contributing to the development of eco-friendly and high-performance electronic devices. Despite advancements, challenges such as achieving uniform filler dispersion and scalability of eco-friendly production methods persist, limiting industrial application
Investigating the synergism and partial replacement of carbon black by cellulose nanofibers in natural rubber-based tyre tread composites
No full textAlleviating the carbon footprint by utilizing bio-based fillers to develop sustainable tyre tread composites is a promising and innovative approach. Our research presents sustainable nanocomposites that utilize cellulose nanofiber (CNF) as reinforcing filler for natural rubber (NR) based truck, bus and radial tyre (TBR) tread composites. The choice of cellulose nanofibers, with their renewable nature, biodegradability, lightweight, and superior mechanical properties, to partially replace carbon black (CB) in different ratios underscores the innovative nature of our approach. Although there are a few studies focused on replacing CB with nanocellulose, a comprehensive study is necessary to optimize the loading of CB and CNF by varying the replacement ratios, thereby fully harnessing the potential of CNF. We have explored the synergism between CB and CNF and optimized CB content in the hybrid nanocomposite, demonstrating a reduction in the amount of CB in tyre tread composites. The performance of the hybrid nanocomposite is shown to be highly dependent on CNF and its concentration, as evidenced by morphological, static and dynamic mechanical properties. The increase in tensile strength and modulus (an increase of 413 % at 100 % elongation) after partially replacing CB by CNF of half the concentration of replaced CB indicates good synergism and better reinforcing ability of CNF. The remarkable decrease in rolling resistance (34 %) and the improvement in wet grip properties after partially replacing CB with CNF is quite promising for tyre tread applications to replace CB with CNF at higher ratios. The lower surface roughness values observed for 2.5 phr CNF-loaded hybrid nanocomposite from AFM analysis indicated better CNF dispersion at lower loadings. The development of these nanocellulose-based tyre tread composites not only offers a sustainable solution but also imparts bioeconomy concepts to tyre industries, reducing their dependence on non-renewable petroleum-based products and opening up new circular economic opportunities
Contrôle des lieux de privation de liberté par les bâtonniers : le Conseil constitutionnel demande au législateur de revoir sa copie
No full textInternational audienc
Navigating Eco‐Social Policymaking: Trends, Drivers, and Barriers. Introduction to the Special Issue
No full textInternational audienceIn recent years, research on the integration between social and ecological policies has significantly expanded, highlighting the multiple ways in which these two domains interact. Concepts such as "just transition" and "sustainable welfare" have gained prominence as normative frameworks capturing these interconnections. However, despite the increasing scholarly attention, several important theoretical, conceptual, and empirical gaps remain, particularly regarding how social and ecological spheres intersect across different political systems. This Special Issue contributes to this debate by exploring the complex policymaking dynamics underlying eco-social policies. Before presenting the contributions, this introductory article provides a thorough review of existing studies on eco-social policies. The review serves a dual purpose: first, it synthesizes existing knowledge, identifying key gaps; second, it allows us to develop a comprehensive framework to understand eco-social policymaking, based on a political system or systemic approach. This framework conceptualizes eco-social policies as the output of a process driven by escalating eco-social risks and concerns. Citizens' attitudes and voting behavior regarding social and environmental policies serve as the initial inputs that shape policy outputs. Within this system, eco-and welfare regimes represent the broader institutional contexts in which political parties and organized interest groups compete to find solutions to eco-social conflicts and eventually supply eco-social policies
La sanction du comportement fautif d'un agent doit aussi tenir compte de sa manière de servir
No full textInternational audienceObservations sous TA Châlons-en-Champagne, 10 mars 2025, no 240057
Improving bond performance of 3D-printable earth-based mortar reinforced with jute fibers
No full textInternational audience3D printing technology has transformed the construction industry by enabling rapid and cost-effective production of complex geometries. However, it faces significant challenges, including sustainability concerns due to cement's environmental impact and reinforcement issues arising from the incompatibility of traditional steel. These challenges necessitate the development of innovative material solutions. This study aims to enhance the bond strength between sustainable earth-based mortar and jute fibers used as reinforcement in 3D printed structures by exploring the effects of different treatments and compositions. Bond strength was evaluated by considering the effect of different treatments on the resistance of the fiber to being pulled out of the mortar. Pull-out tests were conducted on specimens with varying compositions and treatments. Results demonstrated substantial improvement in bond performance; specifically, the reference sand-free earth-clay mortar exhibited the lowest interfacial shear strength of 0.30 MPa. The most remarkable enhancement was observed in specimen which jute fibers pre-treated by immersion in mud slurry, which showed a 147% increase, reaching an interfacial shear strength of 0.74 MPa. Combining sand addition and fiber pre-treatment, however, did not yield additional benefits. These results indicate that simple, cost-effective local treatments can notably enhance fiber-matrix bond strength in 3D-printed earth-based structures without necessitating additional equipment or significant expense
Alternative Printing Methods for Cementitious Materials
No full textInternational audienceRobotic concrete construction goes beyond the technique of depositing successive layers or filaments, which then solidify. In the field of construction materials, 3D printing technologies are multiple and not limited to extrusion 3D printing. Spatial resolution and absolute freedom of form can be achieved by alternative 3D printing techniques, which we will discuss in this chapter. Large-scale 3D printing projects for new housing, structures (like pedestrian bridges) or smaller scale equipment and street furniture are currently being carried out using 3D extrusion printing. Their number is currently growing, and they require R&D before they can be marketed. In terms of the number of construction sites, the main applications of 3D printing are limited to relatively simple shapes with little variation in cross-section, and optimized material quantities that are not always financially or environmentally profitable